This disclosure relates to the field of Magnetic Devices, and such devices include, but are not limited to: (1) various designs of Magnetic Random Access Memory (MRAM), e.g., In-plane or Out-of-plane (PMA) Spin-Torque-Transfer (STT) RAM, (2) various designs of Spin Valve read head or sensor, and (3) other Spintronic devices.
For spin torque applications, the dry etching process of MTJ fabrication will be very critical to the MTJ performance. There are some potential concerns induced by MTJ etching processes such as the following: (A) Sidewall damage during MTJ etching, and (B) Oxidation of sidewall in between the process from MTJ etching to the encapsulated layer deposition (with vacuum broken). These kinds of damage will be more critical as MRAM technology goes toward the 45 nm node or smaller.
In the meantime, this kind of sidewall damage layer around the MTJ is believed to be a chemically unstable layer. The thermal treatment of the semiconductor BEOL (back end of line) process will enhance the sidewall damage due to atom diffusion from the sidewall which will dramatically degenerate MTJ performance.
The present disclosure provides an improved method to fabricate the STT-RAM or related spintronic device with a combination of plasma treatment and in-situ encapsulation layer after the conventional MTJ RIE etching process.
Several patents show cleaning and in-situ deposition. These include U.S. Pat. No. 7,993,535 (Jiang et al), U.S. Pat. No. 8,912,012 (Li et al), and 2014/0263668 (Lee et al).